A global survey says standards in reading, maths and science are falling.
Welfare Families 'Left Worse Off'
Families in Scotland are being affected by Westminster's changes to the benefit system, according to ministers.
A Scottish Government report looked at the impact of changes to benefit uprating implemented by the UK government since 2010-11.
The changes are expected to reduce welfare expenditure in Scotland by around £6 billion over the six years to 2015-16, it is claimed.
This will result in families with two children receiving child benefit being £1,100 worse off over that period, the Scottish Government said.
Mothers claiming statutory maternity pay will lose out on around £330 in the next financial year as a result of changes to uprating of the payment, ministers said.
Deputy First Minister Nicola Sturgeon, who is addressing the annual Poverty Alliance conference today, said the UK government's benefit reform programme "unfairly impacts on some of the most vulnerable members of our society" and claimed welfare cuts hit mothers and their children hardest.
Looking ahead, she said: "Nearly every household in Scotland in receipt of a working age benefit will be affected by plans to introduce a two-year benefit freeze. These planned changes will see Scotland's benefit expenditure reduced by around £300 million in 2017-18.
"These welfare changes do not work for the people of Scotland. Poverty increased in Scotland in 2012-13 for the first time in a decade - an increase that is expected to continue.
"An additional 100,000 Scottish children will be living in poverty by 2020 because of UK welfare reforms and this is before the next round of cuts due in 2017-18.
"This is a direct result of choices made by the UK government - for example, since April 2012, the number of children whose families receive in-work tax credits has decreased by 120,000.
"It is unacceptable that due to the decisions of the UK government children and families in Scotland are suffering."
Ms Sturgeon called for Holyrood to have full powers over welfare and social policy, a proposal which forms part of the administration's submission to the Smith Commission looking at further devolution for Scotland.
Peter Kelly, director of the Poverty Alliance, said: "Poverty is the biggest issue Scotland faces, and with one in five children growing up in poverty it is impossible to ignore."
A spokesman for the Department Work and Pensions (DWP) said: "This government inherited a benefits system in meltdown which trapped the very people it was meant to help.
"Our welfare reforms are transforming the lives of some of the poorest families in our communities and the employment rate in Scotland now at the highest rate since 2008.
"We continue to have a strong safety net in place and benefit spending in Scotland was over £14bn last year."
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